In recent years, a hermetic compressor designed to run silently has highly been required. In conventional hermetic compressors, muffling functions built on an intake muffler attenuate intake pressure pulsing-caused noise. One such example of a conventional hermetic compressor is disclosed in U.S. Pat. No. 5,443,371.
The conventional hermetic compressor will now be described with reference to the drawings. FIG. 8 is a cross-sectional view, illustrating an essential portion of the compressor. In FIG. 8, reference numeral 1, 2, and 3 denote a compression element placed in a hermetic vessel, a cylinder block, and a cylinder that forms a compression chamber 4 of the compression element 1, respectively. Reference numerals 5, 6, and 7 identify a piston reciprocating in the cylinder 3, a valve plate for sealing the cylinder 3 at one end thereof, and an intake valve port formed on the valve plate 6, respectively. The intake valve port 7 is opened and closed by an intake reed 8. Reference numerals 9 and 10 designate an intake muffler and a cylinder head, respectively. The cylinder head 10 secures the valve plate 6 to the cylinder 3 at one end thereof, and further fixes the intake muffler 9 to the intake valve port 7.
A description will now be made as to how the hermetic compressor as structured above (hereinafter called a compressor) operates. A refrigerant gas returned to the compressor from the refrigerant cycle is released into the hermetic vessel. The refrigerant gas is then admitted into the compression chamber 4 through the intake muffler 9 and the intake valve port 7. The cylinder 3 and the piston 5 form the compression chamber 4. The piston 5 reciprocated by rotation of an electrically actuated element compresses the admitted refrigerant gas before the compressed refrigerant gas is fed to the refrigerant cycle through an exhaust pipe.
At this time, a resonance sound in the compression chamber 4 and intake pressure pulsing that occurs at the intake valve port 7 because of the opening/closing of the intake reed 8 are attenuated through the intake muffler 9 before being released into the hermetic vessel, thereby making it possible to reduce noise.
However, such a conventional structure as discussed above has drawbacks that the muffling functions (an expansion chamber and a resonance chamber) of the intake muffler 9 fail to provide a sufficient muffling effect because these are remote from sources such as the compression chamber 4 and the intake valve port 7, and further that acoustic characteristics of the muffler 9 for connecting the intake valve port 7 and the muffling functions together are likely to amplify noises having specific frequencies.
In order to overcome problems heretofore encountered, the present invention provides a low noise compressor designed to allow the resonance sound in the compression chamber 4 and the intake pressure pulsing occurring at the intake valve port 7 because of the opening/closing of the intake reed 8 to be dampened more operatively at a position adjacent to the sources.
Another drawback to the above conventional structure is that an arrangement of the muffling functions being positioned only within the intake muffler 9 causes the expansion chamber and the resonance chamber to be located in a limited space, thereby insufficiently combating noises having several frequencies.